ray-trace or mkillum for external blinds

Hello Radiance community

I would like to ask you what is the best way to simulate external blinds in Radiance. I have tried both full ray-tracing and the mkillum approach but they do not yield the same illuminance values on the working plane. Especially close to the window (0.5-1m) large differences show up (100%).

What is the physically most accurate method? And if it is ray-tracing how do I obtain smooth results in a reasonable amount of time?

Best regards

Christian Hviid

Technical University
of Denmark

What is "full raytracing" here? I think it is best here to replace the glazing by a mkillum pane and, if the shading system masks the window in a way that you expect variying illumination, subdivide that illum face a bit (see mkillum manpage). Without the illum pane, you might "measure" the max/min values of an inaccurate raytracing, sometimes light sources found, sometimes not, purely by luck :wink:

Simulating Venetian Blinds takes a lot of time if you are using 'pure'
Radiance but it is possible. See e.g.:Reinhart C F, Walkenhorst O,
"Dynamic RADIANCE-based daylight simulations for a full-scale test
office with outer venetian blinds." Energy & Buildings, 33:7 pp.
683-697, 2001.

Incidentally, for those of you interested, we have developed a new
daylight coefficient approach where you can simulate a space without
blinds and then multiply your resulting daylight coefficients with a
correction matrix to account for blinds. A rudimentary description of
the method can be downloaded from:
http://lightswitch.irc.nrc.ca/website/p461v1.pdf
<http://lightswitch.irc.nrc.ca/website/p461v1.pdf>

Christoph

ยทยทยท

________________________________

From: [email protected]
[mailto:[email protected]] On Behalf Of
Christian Anker Hviid
Sent: Friday, July 13, 2007 11:40 AM
To: [email protected]
Subject: [Radiance-general] ray-trace or mkillum for external blinds

Hello Radiance community

I would like to ask you what is the best way to simulate external blinds
in Radiance. I have tried both full ray-tracing and the mkillum approach
but they do not yield the same illuminance values on the working plane.
Especially close to the window (0.5-1m) large differences show up
(100%).

What is the physically most accurate method? And if it is ray-tracing
how do I obtain smooth results in a reasonable amount of time?

Best regards
Christian Hviid
Technical University of Denmark